Bones from an ancient woman who lived on Southern California's Channel Islands are probably 13,000 years old, bolstering theories that the first settlers in North America may have been Polynesians or southern Asians who came to the continent by boat, scientists said.

The tests, researchers said, show that the bones of the so-called Arlington Springs woman may be several hundred years older than North America's oldest- known human skeletons, which had been previously discovered in Montana and the Midwest.

The finding challenges established theories that the first settlers came to North America roughly 11,500 years ago from northern Asia using a land bridge to Alaska.

Many scientists had believed until re

cent years that the first visitors walked from Siberia to Alaska across a bridge of land now covered by the Bering Strait, journeying south and east. A popular theory had been that settlers did not populate the continent until the end of the last ice age about 11,500 years ago.

But alternative theories have suggested that the first inhabitants came by boat much earlier than that. The age of the ancient woman's bones and the fact that they were discovered on an island, scientists said, add further support to those theories.

"It's one more piece to the puzzle," said John Johnson, curator of anthropology at the Santa Barbara museum and a member of the research team that helped establish the age of the woman's bones.

"Each find like this adds one more ingredient to helping to reconstruct what life was like back then."

The team's research was published in a paper last month for an islands symposium held at the Santa Barbara museum and will soon be published in national scientific journals.

Other members of the team included scientists from UC campuses in Irvine, Davis and Santa Barbara, as well as experts from Channel Islands National Park and bone analysis specialists from the Stafford laboratories.

1959 DISCOVERY

Two of the woman's thigh bones were discovered in 1959 at Arlington Canyon on Santa Rosa Island near Ventura County. Scientists recently subjected the bones to radiocarbon and DNA tests that were not available at the time they were found.

Those tests showed that the bones are probably 13,000 years old, roughly 1,400 years older than scientists had previously estimated.

"Our whole intention in this was to see if we could use modern technologies to get at the true age of the bones," Johnson said.

The discovery of just how old the bones were was "actually quite a surprise," he added.

"We didn't set out to do that," Johnson said with a chuckle.

CONFLICTING RESULTS

Researchers performed two sets of tests. The first series showed that the bones were 11,000 years old. A second series, however, gave the age at about 13,000 years.

For the second series, scientists also tested mouse bones and a piece of charcoal found in the soil near where the thigh bones were discovered. Although those tests confirmed the age at about 13,000 years, researchers said precise dates from ancient bones remain a tricky business.

"When you're dealing with very ancient remains . . . there's a little bit of uncertainty," Johnson said. The team plans on conducting further tests on the mouse bones.

Scientists were confident, however, that the discovery offers researchers new information about who the first settlers were and where they came from.

"It's an interesting question: How did people get into the New World originally, and where did they go?" said John Southon, a researcher at Livermore's radiocarbon testing unit who worked on dating the bones.

Similar ancient remains discovered in the United States have sparked controversy in recent years because the skeletons do not resemble those of modern Native Americans, but of Caucasoid peoples, leading to increasing disputes about who, exactly, the first settlers were.

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